High reactance transformer



Aug. 24, 1965 N. OULETTA HIGH REACTANCE TRANSFORMER Filed Aug. 21, 1961w 4 1% 2 2 if 3.

United States Patent ()fiice 5,202,872 HIGH REACTA'N'JE TRANSFORMERNicholas Ouletta, Melrose Park, 111., assignor to Jefferson ElectricCompany, Bellwood, Ill., a corporation of Delaware Filed Aug. 21', 1961,Ser. No. 132,777 8 Claims. (21. 315-177 that provided by a previouslydesigned ballast, it is possible toincrease the dimensions of theballast only in the lengthwise direction. As a result, the length towidth proportions of high wattage ballasts increase more or lessdirectly with the desired increase in wattage with respect to a givenstandard of comparison. However,

it has been found that the open circuit voltage does not 7 increaseproportionally to the turn ratio in this long and narrow type ofballast, due to leakage which takes place, even on open circuit, acrossa Window which is very long with respect to its width. The length towidth ratio of such a window may be as high as 17 to 1, even though thecorresponding ratio of the core structure is less than 4 to 1.

It has been proposed to control leakage reactance by making the primarywinding in two parts, spaced from each other with the secondary windingin between, and by providing suitable leakage paths at each end of thesecondary, which leakage paths are necessary to provide the desiredleakage reactance under operating conditions. However, this arrangementfrequently calls for the use or" shunts, or some other special corestructure arrangernent to provide the desired leakage at two differentplaces.

According to my invention, I have found that the open circuit voltagecan be substantially boosted without providing a special corearrangement to provide for the desired leakage reactance, if only asmall portion of the primary winding is located at the remote end of thesecondary winding and is closely coupled thereto. According to thisarrangement, the leakage path arrangement provided between the mainprimary coil and the secondary coil, which may be either in the form ofa shunt, or coil spacing, or an end-to-end coil arrangement plus slots,is sufiicient to provide the desired leakage reactance during operation.

A further advantage of this invention is that the auxiliary primaryturns may be in the form of a tap in the secondary winding, and sincetheauxiliary primary turns are relatively few in number, the smaller wiresize of the secondary winding is sufficient to accommodate the primarycurrent without causing undue temperature'rise in: that portion of theballast.

Another object of my invention is to provide a ballast which reduces thetendency of the lamps to flicker which often occurs when the opencircuit voltage is not much higher than that required to sustain the arcin the lamps.

Other objects, features, and advantages wiil appear as the descriptionproceeds.

With reference now to the drawings in which like reference numeralsdesignate like parts:

FIG. 1 is a plan view of a preferred embodiment of my invention showingthe core structure of a transformer,

3,202,872 Patented Aug. 24, 1965 the location of the primary-andsecondary coils being shown in dotted lines; and

FIG. 2 is an electrical diagram of the circuit of the transformer ofFIG. 1.

With reference now to FIG. 1 which shows the core structure of the highreactance transformer, reference numeral 1% designates the winding leg,and the reference numerals 11 and 12 designate the yoke portions. Theseelements are built up of laminations of the T and L types.

The resulting shell-type core structure provides windows 13 in which theprimary coil 14 and the secondary coil 15 are located, as shown indotted lines. The space between the coils represents a leakage path 16.The coils are spaced from each other by about one eighth of an inch, andthe paper margins represent another oneeighth of an inch each, with theresult that the convolutions of the coil are actually separated fromeach other by: about three eighths of an inch. Variation of thisdistance will affect the leakage reactance, and in some designs, amagnetic shunt type of leakage path may be substituted.

The leakage path 16 divides the winding leg 10 into a primary coreportion 17 and a secondary core portion 18. One or more bridged gaps maybe located in the secondary core portion 18-, and these are preferablyin the form of circular gaps 19' and 20. The bridged gaps increase thereluctance of the secondary core portion and thus aifect the fluxleakage which occurs in the region of the leakage path 16. in thepresent arrangement, in which the length towidth ratio of the windows 13may be as high as 17 to l, considerable leakage would ordinarily occurall along the length of the window, but as previously indicated, thecoilsare connected in such manner as to reduce the leakage which occursunder open circuit conditions.

The circuit is shown in FIG. 2, and it will be observed that thesecondary coil 15 is provided with a tap C which divides the coil intotwo portions 23 and 24, the latter being referred to as the auxiliaryturns 24-. The coil leads are designated B, C,'and D. The 'coil leads ofthe primary coil 14 are designated A and'B. Points A and C are connectedto the line, and points A and D are connected to the load;

The load comprises two fluorescent lamps 25 and 26 which are connectedin series with each other and in series with an operating condenser 27.A starting condenser 28' is connected across lamp 25. Suitable filamentwindings 29 are connected to the lamp filaments in the conventionalmanner.

It will be seen from the foregoing, that the primary winding includesthe primary coil 14 and the auxiliary turns 24. The secondary windingcomprises all of the turns of the secondary coil 15, and the secondarycircuit includes the primary coil 14 as Well.

- The curved arrow 30 represents the potential drop of the'primarycurrent, whereas the dotted line arrows 31 and 32 represent thedirection of induced voltage. The secondary coil 15 is wound in thereverse direction, with respect to the winding direction of primary coil14, but the coils are additively' connected.

The munber of auxiliary turns 24 represents about twenty to thirtypercent of the total primary turns, and the arrangement is preferablysuch' that the tap C can be rought out from the top layer of thesecondary coil 15. By winding the secondary coil in the reversedirection, the turnsbetween points C and B may be physically located atthe remote end of the: secondary coil. Thus, during open circuitconditions, an auxiliary magnetizing flux is set-upin the remote end ofthe secondary core portion 18 which has been found to be very effectivein reducing the amount of leakage which occurs across the Windows Vat-1.5 amps.

13 during open circuit conditions. Nevertheless, the number of auxiliaryturns is sufliciently small that it does not materially affect theamount of leakage which occurs during lamp operation. Therefore,according to my invention, a core structure which has been designed toprovide the proper amount of leakage for the usual type of coilconnection can be used in a transformer made in accordance with thearrangement shown in FIG. 2.

A commercial embodiment of my invention, suitable for energizing two72-inch rapid start lamps, was constructed according to the following:

The primary coil 14 comprised 266 turns of No. 18

wire.

The secondary coil comprised 1323 turns of No. 19 /2 wire arranged innine layers of 147 turns per layer. The last 70 turns of the top layerwere tapped oil, to provide the auxiliary turns 24. The secondary coilwas about 6% inches long, so that the auxiliary primary 24 Wasdistributed over the remote 2% inches of the secondary coil.

The core structure was approximately 9 /2 inches long and 3 inches wide,and the stack was 1 inches high. The yokes, 11 and 12, were /2 inch wideand the winding secondary core portion 18, measuring from the'centerline of the flux leakage path 16 to the remote'end of the window 13. Theopening 19 had notches 21, each M inch deep, so that the total lengthofthe circular gap 1 9 was 4 inch. r x r V a When the primary winding,14-24, is connected to a 120 volt 60 cycle line, the current in thesecondary circuit is 1.66 amps. The line current is 3.26 amps. Powerfactor is 91 percent, and light is 100% (ASA test).

The voltage drops across points A, B, C, D, and E during lamp operationare as follows;

"AB 95 AC 120 AD 580 AB 249 so 29 BD 496 BE 20 5 CD 469 on 209 DE 528has a crest factor-of 1.78..

Thegstarting voltage of type 72T17 lamps is approximately 445 .volts,and the rated operating voltage is 128 The open circuit voltage acrosspoints AD is 460 and When 'a resonant condenser 33 of .33 mfd. isconnected jacross points B and D as shown in FIG. 2,the identicalballast will start and operate two 96-inch rapid start 7 lamps,type'96T17 P.G:, thelcharacteristics of which are: i

V Starting voltage 555 Operating voltagef a 172 Operatingcurr'ent -a 1.5

.catedherein, the open circuit voltage would b'e about 425.volts, whichis insufiicient to start a 72 inch lamp.

The arrangement of my invention increases the'open circuit voltage by atleast 8% without requiring redesign of the core structure or adjustmentof the turn ratio.

Also, my invention materially reduces the tendency to lamp flicker whichis a serious problem when higher wattage ballasts are designed tostandard channel dimensions.

It will be understood that the core and coil structure is potted andenclosed in a steel casing in the usual manner, together with thecondensers.

Gther arrangements may be provided in which it is not necessary toreverse the winding direction of the secondary coil, but'the FIG. 2embodiment is preferred from the viewpoint of cost because it permitsthe use of a tap instead of a separate coil of 70 turns.

For instance in one such arrangement the auxiliary turns may be in theform of a small, narrow coil located at the remote end of the secondarycoil and closely coupled thereto, but not included in the secondarycircuit. The uniform winding direction permits the usual end-toend typeof auto-transformer connection between the primary and secondary coils.

V The characteristic of the resonant or harmonic condenser 33 is that arelatively high volatge drop is developed across it at harmonicfrequencies, such as the third or fifth harmonic,which.voltage dropcooperates with the voltage boost providedby the auxiliary turns 24 toprovide the higher starting voltage required by the 96 inch lamps.

Although only :a preferred embodiment of my invention is shown anddescribed herein, it will be understood that various modifications andchanges may be made in the construction shown without departing from thespirit of my invention as pointed out in the appended claims.

I claim; A 1. A high reactance transformer for use in energizing aleading lamp load of the gaseous discharge type cornprising a corehaving a winding leg and a yoke cooperating with each other to provide along narrow window,

' liary turns, said secondary coil being connected in autotransformerrelationship to said primary coil, said pri mary and secondary coilsbeing loosely coupled to each other to provide high leakage reactanceduring lamp operation, and said secondary coiland said auxiliary turnsbeing tightly coupledto each other. V a

2.. high reactan ce transformer as claimed in claim '1 in which saidsecondary coil is reversely wound with 'respect'to said primary, coil,and said auxiliary turns represent a tapped portion of said secondarycoil. 3. A high reactance transformer as clairned in claim 2 in whichsaid tapped portion is locatedentirely in the outer layer of saidsecondary coil and comprises substantially 25 percent of the turns ofsaid primary coil. 4. A high reactance transformer as claimed in claim 1in whichthe turn ratio of said. primary winding to said secondary coilis substantially one to four.

5. A high reactance transformer asclaimed in claim l in which the lengthto width proportions of said window are substantially seventeen to. one.6. A high reactance transformer as claimed in claim :1 in whichsaidwinding legincludes a bridged gap formed in the secondary portionthereof.

f '7. A high reactance transformer for use in energizing a leading lampload of the gaseous discharge type comprising a core having a windingleg and a yoke cooperating with each other to provide a long narrowwindow, primary and secondary coils located, side by side on saidwinding leg to provide loose coupling therebetween, a plurality ofauxiliary turns closely coupled to said secondary coil, and meansconnecting said auxiliary turns 5, in series with said primary coil toprovide a primary winding which includes said primary coil and saidauxliary turns, said auxiliary turns representing less than 30% of thetotal primary winding turns, and said secondary coil being connected inauto-transformer relationship to at least a portion of said primarywinding.

8. A ballast for energizing a fluorescent lamp load including a highreactance transformer and a series connected operating condenser, saidhigh reactance transformer comprising an elongate type core structurehaving a winding leg and oppositely disposed yokes, primary andsecondary coils disposed on said winding leg in side by siderelationship, a bridged gap formed in said winding leg at a pointwherein it is completely surrounded by said secondary coil, saidsecondary coil being tapped to provide an auxiliary turns portion whichis located at the remote end of said secondary coil, said auxiliaryturns portion being additively connected to said primary coil to providea primary winding, lead means connecting said secondary coil to saidprimary winding in auto-transformer relationship to provide a secondarywinding, a fluorescent lamp load means including said series connectedoperating condenser for connecting said secondary Winding to afluorescent lamp load to provide a secondary circuit, and a harmoniccondenser connected across said secondary coil.

References Cited by the Examiner UNITED STATES PATENTS 2,465,031 3/49Nathanson 315-177 X 2,791,726 5/57 Feinberg 315-239 2,813,228 11/57Feinberg 315239 X 3,061,759 10/62 Spector 315257 JOHN W. HUCKERT,Primary Examiner.

GEORGE N. WESTBY, JAMES D. KALLAM,

Examiners.

8. A BALLAST FOR ENERGIZING A FLOURESCENT LAMP LOAD INCLUDING A HIGHREACTANCE TRANSFORMER AND SERIES CONNECTED OPERATING CONDENSER, SAIDHIGH REACTANCE TRANSFORMER COMPRISING AN ELONGATE TYPE CORE STRUCTUREHAVING A WINDING LEG AND OPPOSITELY DISPOSED YOKES, PRIMARY ANDSECONDARY CLILS DISPOSED ON AID WINDING LEG IN SIDE BY SIDERELATIONSHIP, A BRIDGED GAP FORMED IS SAID WINDING LEG AT A POINT WHERINIT IS COMPLETELY SURROUNDED BY SAID SECONDARY COIL, SAID SECONDARY COILBEING TAPPED TO PROVIDE AN AUXILLIARY TURNS PORTION WHICH IS LOCATED ATTHE REMOTE END OF SAID SECONDARY COIL, SAID AUXILLIARY TURNS PORTIONBEING ADDITIVELY CONNECTED TO SAID PRIMARY COIL TO PROVIDE A PRIMARYWINDING, LEAD MEANS CONNECTING SAID SECONDARY COIL TO SAID PRIMARYWINDING IN AUT-TRANSFORMER RELATIONSHIP TO PROVIDE A SECONDARY WINDING,A FLOURESCENT LAMP LOAD MEANS INCLUDING SAID SERIES CONNECTED OPERATINGCONDENSER FOR CONNECTING SAID SECONDARY WINDING TO A FLOURESCENT LAMPLOAD TO PROVIDE A SECONDARY CIRCUIT, AND A HARMONIC CONDENSER CONNECTEDACROSS SAID SECONDARY COIL,